1. Field of the Invention
The present invention generally relates to electrically-driven riding mowers for use on golf courses and other large grounds, and more particularly relates to electrically-driven riding mowers which are steered in a fly-by-wire mode so that operator provided input to the steering system is electronically detected by a controller which generates control commands to a steering motor to displace a steerable wheel to guide the mower.
2. Discussion
The assignee of the present invention recently introduced an all-electric riding greens mower. The mower of this all-electric riding greens mower is described in detail in commonly-assigned U.S. patent application Ser. No. 08/191,553, filed Feb. 3, 1994, now U.S. Pat. No. 5,406,778, issued Apr. 18, 1995, the disclosure of which is hereby incorporated by reference. The triplex riding mower disclosed in this co-pending application has a bank of batteries supported near the rear of the frame of the riding mower which provides electrical power for operating the main drive electric motor, three reel motors, and three lift motors for raising and lowering the reel type mowing heads as needed. The main motor drives a transaxle that provides a driving force to the two forward wheels of the triplex mower. The three reel mowers each directly drive one of the reels, which may be operated independently. The three lift motors individually drive a screw-type lift mechanism which raises and lowers a head much the same way that conventional hydraulically-powered single-rod cylinders do. The mower includes a foot pedal controlled by the operator which actuates a potentiometer which directs forward or reverse motion of the vehicle at any desired rate of speed, within the limits permitted by the drive motor control circuitry and by the power capabilities of the main motor and batteries. Heavy duty contactors switchably apply electrical energy to the reel motors, which are provided with the full voltage of the battery pack, which is nominally 48 volts obtained by eight 6-volt batteries wired in series.
There are numerous advantages to using an all-electric riding greens mower. These include very quiet operation, because there is no noisy internal combustion engine. Another advantage is the absence of hydraulic devices and accompanying hydraulic oil on the machine, which eliminates the possibility of hydraulic oil leaks. As is known, hydraulic oil leaks in conventional hydraulically-driven and hydraulically-powered turf care equipment can significantly damage a golf green or fairway if undetected by the mower operator.
Another major advantage of the all-electric greens mower is that it does not produce byproducts of combustion, and thus can operate in areas where the use of conventional internal combustion powered mowers is prohibited due to pollution concerns and regulations.
While the disclosed all-electric greens mower is quite satisfactory and much appreciated, it is difficult and impractical to mow large areas, such as fairways or parks with that style of mower, even when appropriate reel-style mowing heads are installed. The range of the battery packs carried by the present mowers remain inherently limited by the power capabilities of conventional batteries.
One challenge presently faced by many golf course operators is that municipalities and communities, especially those which have residential homes bordering the golf courses, restrict by ordinance the hours during which the fairways and greens may be mowed. Homeowners have tired of noisy mowing equipment awakening them during the early morning hours, between 5:00 a.m. and 8:00 a.m., and disturbing them in their leisure during the later evening hours, between 7:00 p.m. and 10:00 p.m., when they expect peace and quiet in their neighborhoods. Golf course operators, on the other hand, dislike mowing their courses during peak golfing times, between 7:00 a.m. and 7:00 p.m. during the golfing season. This challenge presents particular difficulties for golf course owners whose courses are continuously busy, and usually have a waiting list of people seeking tee times.
A sufficiently quiet mower, such as an all-electric mower would allow for mowing fairways and greens on golf courses even where communities have instituted noise-limiting ordinances. This is because the all-electric mowers are very quiet. Unfortunately, the battery range of a riding electric mower with one bank of batteries (even though the battery weight is in excess of 400 pounds) is limited. Battery-powered commercial mowers, therefore, remain impractical for mowing large areas due to the typically extensive recharge times required to fully recharge the battery and the undesirable need to interrupt the mowing process (which the golfers wish to have completed as expeditiously as possible) while the batteries are re-charging.
Therefore, it is a principal object of the present invention to provide an electrically-operated riding mower capable of mowing large areas of turf, such as golf course fairways, soccer fields, parks, and municipal grounds while producing very little noise and minimizing mowing interruptions to re-charge the on-board batteries. A related object is to provide an all-electric riding mower which is capable of being used to mow large areas.
Yet another object of the present invention is to provide an electrically-driven mower which utilizes a motor generator as an electrical energy source which operates in a quiet, highly efficient manner in order to conserve fuel and variably deliver electricity on a demand basis to the electrically-driven mower.
Yet another object is to provide a comparatively lightweight electric mower powered by a motor-generator set. A further object is to provide a hybrid fairway mower which utilizes electric motors for the main drive and the reel-style mower heads, while using electro-hydraulic power for the mower head lift mechanisms and steering.
Yet another object is to provide an extremely quiet, long-life motor-generator set arrangement adapted for use on a fairway mower.
Yet another object is to provide an advanced microcomputer-controlled system for efficiently operating a motor-generator set even when mowing or traveling at different ground speeds.
Yet another object is to provide a microcontroller-based electronic control system for operating electrically-driven riding mowers with multiple-mowing heads.
Yet another object is to provide an electrically-driven mower which conserves the amount of fuel required to operate motor-generator set by operating the motor-generator at substantially peak efficiency at all times.
Still further objects of the present invention are set forth in and will become apparent from the following summary of the invention and the detailed description and claims thereafter.